Many developing countries are increasingly using tourism as a tool for regional development. While it is expected that tourism can bring substantial benefits, there is also evidence that it can entail negative social, cultural and environmental impacts, and clearly tourism at the regional scale requires careful planning in order to promote sustainable development. While tourism has been planned for decades, there has been relatively little research on how to plan for tourism development at the regional scale in either developing or developed countries. There is growing acceptance that tourism planning at all geographical scales ought to involve broad participation so that the affected stakeholders are engaged in the decision-making. However, research on stakeholder participation in tourism planning has only very recently begun to draw on the valuable insights offered by collaboration theory. This research examines stakeholder participation in tourism planning based on a case study of the Costa Dourada project, a regional tourism initiative involving ten very poor municipalities in Alagoas State in north-east Brazil. The project sought to combine regular collaborative planning meetings involving a range of key stakeholders with consultation with a much larger number of parties affected by the project. The study examines the participation processes involved in the collaborative planning process, the extent to which collaboration fully emerges in the planning process, and the views of stakeholders not involved in the collaborative planning about the project and the planning process. Additionally, consideration is given to the extent to which the planning process was likely to promote co-ordinated planning and concern for the varied issues affecting the sustainable development of the region. The approach to the study was based on a conceptual framework that will be of use to other researchers, this being developed from literature on collaboration theory, stakeholder participation in tourism planning, regional tourism planning and sustainable tourism planning. Importantly this framework can be applied to other regional tourism planning contexts. Data for the study was collected from primary documents related to the project, two semi-structured interviews and two structured questionnaires, and from observation of planning activities. The planning issues and the planning process were evaluated from the perspectives of both participants in the regular collaborative planning meetings and also other stakeholders affected by the project. The results suggest that the approach to regional tourism planning adopted in the Costa Dourada project encouraged a reasonably co-ordinated response from a 'broad range of stakeholders whose interests were largely focused either at local, state and national geographical scales. The regional planning process adopted by the project helped the federal government to share power and decision-making with state and local governments. Participants in the collaborative planning were engaged in negotiation, shared decision-making and consensus building and most were broadly supportive of the project aims, decision-making, and decisions. However, some participants had significant concerns, such as about the extent to which everyone's views were taken into account. The way in which collaborative and consultative approaches to participation were combined was relatively successful in helping to identify key stakeholders and issues, in raising awareness about the project and building external support for the project. The range of participants in the project planning was also likely to promote consideration of many of the issues of sustainable development, although there was only limited involvement of environmental groups and of private sector interests. The study develops a new conceptual model of the collaborative process in regional tourism planning which was developed deductively from relevant academic literature and also inductively from the Costa Dourada case study. The model integrates collaborative and consultative approaches to tourism planning and relates these to broader influences. One contribution of the study is that it identifies stages in the collaborative process but stresses that these substantially overlap and there are dynamic and iterative links between them. Key issues for a theoretical understanding of collaborative regional tourism planning are also evaluated.